Light sensitive photographic color element



April 27, 1965 J. F. WILLEMS ETAL 3,180,734

LIGHT SENSITIVE PHOTOGRAPHIC COLOR ELEMENT Filed Nov. 7. 1960Wlllllllllll/MIIA Meg/afer n INVENTORS BYM, wei-v ATTORNEYS UnitedStates Patent O 3,180,734 LIGHT SENSITIVE PHOTOGRAPHS CGLOR ELEMENTJozef Frans Willems and Willem Karel Koerber, both of Wilrijk-Antwerp,Belgium, assignors to Gevaert Photo- Producten NN., Mortsel, Belgium, aBelgian company Filed Nov. 7, 1960, Ser. No. 67,483 Claims priority,application Belgium, Nov. 5, 1959, 39,339, Patent 584,331 4 Claims. (Cl.96--74) This invention relates to a process for improving the colorreproduction of a color photographic material.

When preparing photographic color images by color development of exposedsilver halide layers, a silver salt image and a color image are formed,the latter being formed by the reaction of the oxidation productsV ofthe color developing substances such as the usual p-dialkyl phenylenediamines with a color coupler present in said silver halide layer toform a dye.

In the color development of a color photographic material which iscomposed of different layers, and which comprises three silver halidelayers respectively sensitized for the blue, green and red regions ofthe spectrum, and which also contain a color coupler forming,respectively, a yellow, a magenta and a cyan dye with the oxidationproducts of the developer, it is oi' paramount irnportance that theoxidation products of the developer, which are formed in a delined layerby the reduction of the exposed silver halide in said layer, couples insitu with the color coupler present therein.

Although in most cases the greater part of the formed oxidation productscouples in situ, a rather important part of these products diffuses toan adjacent layer to couple with another color coupler present thereinresulting into an undesirable color whereby a bad color reproduction isobtained.

The same phenomenon appears in a photographic material which is suitablefor the manufacture of color images wherein for instance three silverhalide emulsions in a water-soluble binding agent, one of which isred-sensitized, one green-sensitized and one blue-sensitized, which forinstance contain all three a color coupler and which form With theoxidizing products of the developer respectively a cyan-, a magentaand ayellow dyestufi, are dispersed in a solution of a water-insoluble butwaterpermeable full-synthetic macromolecular compound whereafter thedispersion thus obtained is applied to a suitable support. Thepreparation of such photographic material suitablevfor thev preparationof color image is described in the Belgian patent specification 536,673.

A variant of this process consists in preparing a dispersion of silverhalide grains in an aqueous solution of a hydrophilic binding agent, toemulsify this dispersion in a solution of -a hydrophobic binding agentin an organic solvent which is not miscible with water, and to emulsifythereafter the emulsion thus obtained in anaqueous solution of ahydrophilic layer-forming binding agent. This method is described in theBelgian patent speciiication 551,312.

Still other -variants are:

A photographic emulsion prepared in a water-insoluble butwater-permeable binding agent is dispersed in a water-soluble bindingagent, e.g. gelatin or polyvinyl alcohol (US. patent specifications2,490,749 and 2,548,526).

A dispersion of a modiiied (in situ selectively hardened orinsolubilised by cross-linking) originally in watersoluble photographicemulsion (among others gelatin in a water-soluble binding agent) (US.patent specilication 2,698,794). K

A dispersion of a photographic emulsion, prepared in a suitablewater-soluble binding agent, in a water-soluble lflgd Patented Apr. 2?,i965 ICC binding agent which is not compatible with the first (eg.

gelatin and polyvinyl alcohol) (British patent specification 800,444).

A dispersion of silver halide gelatin emulsion in cellulose-ether (outerphase) (Belgian patent specifications 520,567 and 542,381).

In the processing of such photographic elements for obtaining colorimages, it is likewise of great importance that the oxidation productsformed by reduction of the exposed silver halide, couple on that areawhere they are formed and do not dilluse away to an emulsion dropletwith other properties to form therein an undesirable color.

It is already known that some products belonging to the type of thecyclic compounds containing OH groups (US. patent specifications2,360,290 and 2,401,713) comprising especially the hydroquinonederivatives (Belgian patent specification 447,239, U.S. patentspecification 2,336,327, Belgian patent specilication 453,723, U.S.patent Specifications 2,403,721, 2,675,314, 2,701,197, 2,704, f

713, 2,710,801, 2,735,765, 2,728,659, 2,732,300), ascorbic acidderivatives (U.S. patent speciiications 2,336,327 and 2,768,661) andfurther hydragine compounds (German patent DBP 984,810) are capable ofreacting with the oxidation products of the color developer.

These reducing agents possess the property of oxidizing more easily thanthe color developing substance itself and, moreover, of not couplingwith the color couplers on color development. When using these compoundsin the color photographic emulsions it is possible to eliminate thegeneral color fog formation which may arise during the color development(c g. by aerial oxidation of the color developer or by oxidation of thecolor developer by the colloidal silver of the yellow filter layer, ifpresent).

However, when these compounds are present in the emulsion layers theyaffect the dye formation between the formed oxidation products of thecolor developer and the color coupler present since a competition arisesbetween the dye formation on the one hand and the reduction of theformed oxidation products on the other hand. Moreover, while the cycliccompounds containing OH groups are quite capable of reducing thediffusing oxidation products of the color developer, they form coloredoxidation products whereby the fog of the iinished color images isincreased in too high an extent.

By making these compounds fast to dillusion and incorporating them intoa thin layer between two differently sensitized silver halide layers oremulsion droplets, it is in principle possible to obtain a better colorreproduction since they react with the diffusing oxidizing products tocolorless compounds and in this way prevent the formation of anundesirable color in another layer, or another emulsion droplet, as thecase may be. Application of this technique, however, has still thedisadvantage that the color fog is strongly increased.

Furthermore the reduction power of the ascorbic acid derivatives and ofthe hydrazine compounds is insufficient so that the color reproductionis not satisfactorily irnproved when such compounds are used. It is alsoknown that ascorbic acid and its derivatives decompose very rapidly andthat their practical utility is but very limited.

Another technique for improving the color reproduction of colorphotographic images has been described in the Belgian patentspecification 560,907. According to this patent, compounds are usedwhich are capable of forming colorless coupling products with theoxidation products of the color developer. For this purpose, cornpoundsare considered having the structure of the usual ketone-methylene colorcouplers for yellow and for rnagenta, one hydrogen atom of the activemethylene group of which having been replaced by an alkyl-, acycloalkyl, an arylor an aralkyl group. These compounds form colorlessproducts with the oxidation products of the color developer.

According to said technique color photographic images with an improvedcolor reproduction can be produced. During storage, however, thesetinished color images soon discolor which is probably due to thedecomposition of the rst formed leuco-derivative in the coloredproducts. This discoloring is particularly well noticeable at increasedtemperatures such as c g, on high-glossing the tinished images.

Now we have surprisingly found that a considerably improved colorreproduction can be obtained without the above-mentioned disadvantagesby adding to the layers present between two differently sensitizedsilver halide layers or to the phase present between the differentsilver halide emulsion droplets, compounds which correspond to one ofthe following general formulae R1 represents a member selected from thegroup consisting of an alkyl group, a substituted alkyl group, an arylgroup, a substituted aryl group, an aralkyl group and a substitutedaralkyl group;

R2 represents a member selected from the group consisting of a hydrogenatom, an alkyl group, a substituted alkyl group, an aryl group, asubstituted aryl group, an aralkyl group and a substituted aralkylgroup;

R3 represents a member selected from the group consisting of a hydrogenatom, an alkyl group, a substituted alkyl group, an aryl group, asubstituted aryl group, an aralkyl group, a substituted aralkyl group, ahydroxyl group, an alkoxy group, an aryloxy group, an amino group, analkylamino group, a hydrazino group and a substituted hydrazinno group;

R4 represents a member selected from the group consisting of an oxygenatom and an oxime group;

X represents a member selected from the group consisting of a hydrogenatom and an acyl radical;

at least two of the radicals R1, R2 and R3 containing a group makingsaid compounds fast to diffusion.

Examples of compounds which correspond to the general formulae of thisinvention are among others: alphahydroxy (or alphaaryloxy)-acyl aceticacid esters II O OH O OCOR and the products which are formed bysaponication or both by saponiiication and dicarboxylation, as well asthe conversion products of these compounds, with amines, hydrazines,hydrazides and sulphonyl hydrazides.

Hereinafter follow some examples of preparation.

PREPARATION 1 CxsHsi-C O-CH-C O 03H5 O C O C H3 37.5 g. of palmitoylacetic acid ethyl ester are dissolved in 100 cm.3 of acetic aciddistilled over potassium permanganate. Whilst thoroughly stirring, 74 g.of lead tetracetate are slowly added. Thereafter the temperature isincreased to 80 C. and stirring is continued for another 1 hour untilthe reaction mixture has cornpletely discolored. The whole is poured outinto 250 cm.3 of water, the precipitate formed is filtered of and washedwith water. The precipitate is dissolved in ether and the insolubleresidue is ltered off. The ether is distilled oit and the residueobtained is recrystallized from methanol. Melting point: at about 24 C.

PREPARATION 2 C15H31--CO--CH2--OH PREPARATION 3 8 g. of the productobtained according to Preparation 1, and 2.55 g. of mono-ethanolamineare heatedfor 6 h. in a flask, cooled ott and recrystallizedfrommethanol. Melting point: 50 C.

This product can be prepared according to the description given in J.Chem. Soc. 1942, page 205.

This compound can be prepared by treating 2 mol of caprylic acid esterwith a sodium dispersion according to I. Am. Chem. Soc., 57 (1935), page2302.

The compounds according to the general Formulae I and IL dissolved in asuitable solvent are mixed with a solution of gelatin or of anotherbinding agent Wherefrom the intermediate layers mentioned hereinbeforeare prepared. In case these compounds are used in a material which iscomposed of dispersed differently sensitized emulsion droplets such asfor instance described in and known from the Belgian patentspecifications 536,673 and 551,312, these compounds can be added to theintermediate discontinuous phases as well as to the outer continuousphases. In case the inner discontinuous phase consists of two colorsensitive emulsions and the hydrophilic outer continuous phase containsthe non-sensitized emulsion and a color coupler for yellow, it isnecessary to add these compounds to the hydrophobic intermediatediscontinuous phase.

The amount is chosen lin such a way that the content of active compoundlays between about 0.025 g. and 2 g. per sq m. of intermediate layerwhich corresponds with a concentration of 0.100 g. to 20 g. per litre of:intermediate layer solution. This concentration is not critical and canif necessary be shifted up to higher limits.

In case the compounds are poorly miscible with the aqueous colloidlayers with which. they are mixed before casting, the compounds can bedispersed therein by means of a suitable emulsifying agent. Verysuitable emulsifying agents are among other sodium salts of alkylbenzene sulphonic acids having surface-active properties.

It is of common practice to apply in the color threelayer material, ayellow filter layer between the bluesensitive layer and thegreen-sensitive layer in order to eliminate the sensitivity to blue ofthe emulsion layers sensitive respectively to green and to red.. Such ayellow iilter layer is usually composed of colloidal silver. In thiscase the compounds according to the present invention can advantageouslybe used in the yellow lter layer since the colloidal silver exercises anoxidizing effect on the usual color developers whereby these oxidationproducts can diffuse to an adjacent emulsion layer to produce anundesirable color. If the compounds according to the present inventionare used, these oxidation products are immediately reduced again wherebytheir noxious f action is excluded.

It is also possible to incorporate these compounds into the silverhalide layers themselves containing the color couplers. In that case,however, the concentration of these compounds must be such that noexcessive competition arises between the dyestui formation of oxidizeddevelopers with the color coupler on the one hand and the reduction ofthe oxidation products on the other hand.

FIG. 1 is a diagrammatic illustration of an otherwise conventionalthree-layer color material in which one of the novel reducing agents ofthis invention is incorporated in the yellow filter layer separating theblue-sensitive and green-sensitive layers and in an interlayerseparating the green-sensitive and red-sensitive layers. FIG. 2 is asimilar illustration of an alternative embodiment in which the severalemulsions are dispersed in a common colloid layer which contains thereducing agent of the invention.

In emulsions which on account of determined causes show an excessivegradation, these compounds can simultaneously be used for regulatingthis gradation.

The following examples illustrate the invention without limiting,however, the scope thereof.

Example 1 A photographic color material which is composed ofrespectively a suitable support, a red-sensitized silver halide layercontaining a colorcoupler for cyan, an intermediate layer consisting ofCompound according to Prep. 1 2 g.

dissolved in 40 cm.3 of Dodecylbenzene sulfonic acid 0.5 g. ethanol.

Gelatin 24 g. Water l l.

Grams p-Diethylamino-aniline sulfate 3 Sodium sulte (anhydrous) 2 Sodiumcarbonate (anhydrous) 60 Potassium bromide 1.5

Water to 1000 cm.

The further finishing process is executed in the commonly known baths.in this -way a color image is obtained showing a much better colorreproduction than the color reproduction of a .color photographicmaterial, simillarly composed and finished but comprising intenlayerswhich were coatedfrom a pure gelatin solution. This improved colorreproduction can e.g. be measured in the following way: a greenselection of the three-layer material to be tested is made. Next, the Hand D-curve of this green-selection is measured behind greenandrediilter in the Ansco-densitometer, and that step of the curves isselected the density of which behind the red filter is nearest to 0.50;the density x behind green filter is measured on the same step. Then iscalculated which percentlage of the unknown density Arepresents thedensity of 0.50; the lower this percentage the better the colorreproduction. Thus, a side-absorption of 37% is noted for color materialcomposed according to the foregoing example and wherein the interlayersare cast only from a pure gelatin-solution whereas an improvedside-absorption of 27% is noted for a material provided with interlayerswhereto the compound 1 has been added.

Example 2 The same photographic color material and processing as inExample l, but instead of 2 g. of the compound according to Preparation1, 1.5 g. of the compound according to Preparation 2 are added to thegelatin intermediate layers. The improved color reproduction obtained isexpressed by a considerably improved measured side-absorption of 23.7%as against 37% of a same material without this compound in theintermediate layers.

Example 5' The same photographic color material and processing as inExample 1, but instead of 2 g. of the co-mpound according to Preparationl, 2 g. of the compound according to Preparation 3 are added to thegelatin intermediate layers and to the yellow filter layer. The improvedcolor reproduction obtained is expressed by a considerably improvedmeasuredside-absorption of 26% as against 37% of a same material withoutthis compound in the intermediate layers.

Example 4 A same photographic color material and processing as inExample l, 'but instead of 2 g. of the compound according to Preparation1, 1 g. of the compound according to Preparation 4 is added to thegelatin intermediate layer and to the yelow filter layer. The improvedcolor reproduction obtained is expressed by a considerably improvedmeasured side-absorrption of 25% as against 37% of a same materialwithout this compound in the intermediate layers.

Example 5 50 cm.3 of a red-sensitized silver chloride emulsion withnormal gradation, containing a color coupler for cyan, are mixed with0.6 cm.3 of 10% aqueous solution of a polystyrene maleic anhydridecomposed of equimolecular amounts of both monomers. 5 g. of thebutyraldehyde polyvinyl acetal known as Pioloform DS (registeredtrademark) .are dissolved in 25 cm.3 of chloroform, 25 cm.3 of amylalcohol and 45 cm.3 of carbon tetrachloride. The photographic emulsionis emulsitied in the polyvinyl acetal solution with a colloid mill or ahomogenizer. In the same way, a green-sensitized silver chlorideemulsion containing a color coupler for magenta is prepared and ablue-sensitive photographic emulsion containing a color coupler foryellow are prepared. Next, each of the emulsions thus obtained is againseparately emulsiiied in 150 cm.3 of a 6% aqueous gelatin solutioncontaining l g. of the compound according to Preparation 1 dissolved in20 em of ethanol. Then these three complex emulsions are mixed andcoated onto a paper support. After exposure, color development as inExample l and lrther finishing, the three different colors are formed inthe three different inner phases. The color reproduction and the colorseparation are much better than in a material which is composed in quitethe same way but wherein no compound was added to the gelatin phase.

Example 6 The same emulsion preparation and the same finishing as inExample 5 but 2 g. of the compound according to Preparation l are addedper each 100 cm.3 of solvent to the hydrophobic phases consisting ofbutyraldehyde polyvinyl acetal. The outer gelatin phase consists of puregelatin. The color reproduction and the color separation are much betterthan when these compounds are not added.

We claim:

1. A photographic color lm comprising a plurality of silver halideemulsions, each of said emulsions being sensitive to a different portionof the spectrum and containing a color coupler capable of coupling withthe oxidation product of an aromatic amino color developing agent, and aseparate colloid phase containing a reducing agent selected from thegroup consisting of a compound of the formula BiC-(IJH-Rz its enolictautomer, and mixtures thereof, wherein an alkyl radical, a carboxyalkylene radical, a lower alkoxy carbonyl radical, and a lower hydroxyalkyl amino carbonyl radical, and

X is selected from the group consisting of hydrogen and a loweraliphatic carboxylic acyl radical.

2. A multilayer photographic color iilrn comprising a plurality ofsuperposed silver halide emulsion layers, each of said emulsions beingsensitive to a different portion of the spectrum and containing a colorcoupler capable of coupling with the oxidation product of an aromaticamino color developing agent, and an intermediate colloid layercontaining a reducing agent selected from the group consisting of acompound of the formula rality of aqueous colloid silver halideemulsions, each ofl said emulsions being sensitive to a dilerent portionof the spectrum and containing a color coupler capable of coupling withthe oxidation product of an aromatic amino color developing agent, asthe phase surrounding the discontinuous inner phase a hydrophobiccolloid and as the continuous outer phase a gelatin layer containing areducing agent selected from the group consisting of a cornpound of theformula Rx-CH-Rz o X its enolic tautomer, and mixtures thereof, whereinR1 is a long chain alkyl radical,

R2 is selectedfrom the group consisting of hydrogen, an alkyl radical, acarboxy alkylene radical, a lower alkoxy carbonyl radical, and a lowerhydroxy alkyl amino carbonyl radical, and

X is selected from the group consisting of hydrogen and a loweraliphatic carboxylic acyl radical.

4. A photographic color iilm comprising a colloid layer which containsas the discontinuous inner phase a plurality of aqueous colloid silverhalide emulsions, each of said emulsions being sensitive to a dilierentportion of the spectrum and containing a color coupler capable ofcoupling with the oxidation product of an aromatic amino colordeveloping agent, as the phase surrounding the discontinuous inner phasea hydrophobic colloid containing a reducing agent selected from thegroup consisting of a compound of the formula Rio-'on-Rz o 0X its enolictautomer, and mixtures thereof, wherein R1 is a long chain alkylradical,

R2 is selected from the group consisting of hydrogen, an alkyl radical,a carboxy alkylene radical, a lower alkoxy carbonyl radical, andra lowerhydroxy alkyl amino carbonyl radical, and

X is selectedfrom the group` consisting of hydrogen and a loweraliphatic carboxylic acyl radical.

References Cited by the Examiner UNITED STATES PATENTS NORMAN G.TORCHIN, Primary Examiner. HAROLD N. BURSTETN, Examiner.

1. A PHOTOGRAPHIC COLOR FILM COMPRISING A PLURALTIY OF SILVER HALIDEEMULSIONS, EACH OF SAID EMULSIONS BEING SENSITIVE TO A DIFFERENT PORTIONOF THE SPECTRUM AND CONTAINING A COLOR COUPLER CAPABLE OF COUPLING WITHTHE OXIDATION PRODUCT OF AN AROMATIC AMINO COLOR DEVELOPING AGENT, AND ASEPARATE COLLOID PHASE CONTAINING A REDUCING AGENT SELECTED FROM THEGROUP CONSISTING OF A COMPOUND OF THE FORMULA R1-CO-CH(-O-X)-R2 ITSENOLIC TAUTOMER, AND MIXTURES THEREOF, WHEREIN R1 IS A LONG CHAIN ALKYLRADICAL, R2 IS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, AN ALKYLRADICAL, A CARBOXY ALKYLENE RADICAL, A LOWER ALKOXY CARBONYL RADICAL,AND A LOWER HYDROXY ALKYL AMINO CARBONYL RADICAL, AND X IS SELECTED FROMTHE GROUP CONSISTING OF HYDROGEN AND A LOWER ALIPHATIC CARBOXYLIC ACYLRADICAL.